benchmark: add benchmark for object properties

Adds a benchmark to compare the speed of property setting/getting in
four cases:
- Dot notation: `obj.prop = value`
- Bracket notation with string: `obj['prop'] = value`
- Bracket notation with string variable: `obj[prop] = value`
- Bracket notation with Symbol variable: `obj[sym] = value`

PR-URL: https://github.com/nodejs/node/pull/10949
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>

benchmark/misc/object-property-bench.js

@@ -0,0 +1,81 @@
+'use strict';
+
+const common = require('../common.js');
+
+const bench = common.createBenchmark(main, {
+  method: ['property', 'string', 'variable', 'symbol'],
+  millions: [1000]
+});
+
+function runProperty(n) {
+  const object = {};
+  var i = 0;
+  bench.start();
+  for (; i < n; i++) {
+    object.p1 = 21;
+    object.p2 = 21;
+    object.p1 += object.p2;
+  }
+  bench.end(n / 1e6);
+}
+
+function runString(n) {
+  const object = {};
+  var i = 0;
+  bench.start();
+  for (; i < n; i++) {
+    object['p1'] = 21;
+    object['p2'] = 21;
+    object['p1'] += object['p2'];
+  }
+  bench.end(n / 1e6);
+}
+
+function runVariable(n) {
+  const object = {};
+  const var1 = 'p1';
+  const var2 = 'p2';
+  var i = 0;
+  bench.start();
+  for (; i < n; i++) {
+    object[var1] = 21;
+    object[var2] = 21;
+    object[var1] += object[var2];
+  }
+  bench.end(n / 1e6);
+}
+
+function runSymbol(n) {
+  const object = {};
+  const symbol1 = Symbol('p1');
+  const symbol2 = Symbol('p2');
+  var i = 0;
+  bench.start();
+  for (; i < n; i++) {
+    object[symbol1] = 21;
+    object[symbol2] = 21;
+    object[symbol1] += object[symbol2];
+  }
+  bench.end(n / 1e6);
+}
+
+function main(conf) {
+  const n = +conf.millions * 1e6;
+
+  switch (conf.method) {
+    case 'property':
+      runProperty(n);
+      break;
+    case 'string':
+      runString(n);
+      break;
+    case 'variable':
+      runVariable(n);
+      break;
+    case 'symbol':
+      runSymbol(n);
+      break;
+    default:
+      throw new Error('Unexpected method');
+  }
+}